Polycarbonates are well known thermoplastic materials which, due to their many advantageous properties, are used as thermoplastic engineering materials. The polycarbonates may generally be prepared by the reaction of a carbonate precursor such as phosgene with a dihydric phenol such as bisphenol-A. These polycarbonates exhibit, for example, excellent properties of toughness, flexibility, optical clarity, and good heat distortion temperatures. However, in certain applications better impact properties than those possessed by conventional polycarbonates are required. lt is known that the impact properties of polycarbonates may be improved by blending with the polycarbonate resins certain impact modifiers. While the resultant compositions exhibit better impact properties than the unmodified polycarbonate resin alone, the use of impact modifier additives suffers from several disadvantages such as the fact that some of these impact modifiers tend to adversely affect the optical properties, such as transparency, of the polycarbonates.
It would be very advantageous if polycarbonates could be provided which exhibit improved impact properties and simultaneously retain the quite excellent optical properties of these conventional polycarbonate resins. It is, therefore, an object of the invention to provide carbonate polymers exhibiting improved impact properties.